Computed Unsteady Structure of Spiral Vortex Breakdown on a Delta Wing

The influence of secondary flows on the performance of turbines has been investigated in great detail in the last decades. The interaction of vortices with following blade rows has been identified to be one of the loss mechanisms within a turbo-machine. This paper presents for the first time detailed flow visualization photographs of the interaction of the vane passage vortex with the rotor. The appearance vortex breakdown could be identified before and within the rotating passage of the turbine. The measurements were taken in a vertical water channel. Water is used instead of air because the flow visualization can be realised very easily with injected ink. For different relative positions of rotor to stator a series of photographs were taken. With an image editing process the average and the pixel RMS were calculated for each relative position. The pixel RMS is a useful indicator to identify highly turbulent regions in the flow field. The photographs of the vortex breakdown show spots of high pixel RMS which are associated with very high turbulence and therefore can be regarded as sources of loss. Insight is gained into the nature of the passage vortex breakdown mechanisms as follows: first the pressure wave of the rotor stretches the vortex causing a spiral vortex instability, then the vortex interacts with the leading edge as it attempts to cut the vortex. In the stagnation region of the blade a bubble type instability forms, expands and then convects through the rotor. The absolute trajectory of the vortex fluid reveals that it exchanges no work with the rotor.

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Vortex Breakdown on a Delta Wing

The Physics of Fluids ◽

10.1063/1.4738804 ◽

1986 ◽

Vol 29 (9) ◽

pp. 2773-2773

Author(s):

F. M. Payne ◽

R. C. Nelson ◽

T. T. Ng

Keyword(s):

Vortex Breakdown ◽

Delta Wing

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Aerodynamic characteristics of delta wing–body combinations at high angles of attack

The Aeronautical Journal ◽

10.1017/s0001924000049848 ◽

1994 ◽

Vol 98 (975) ◽

pp. 159-170 ◽

Cited By ~ 1

Author(s):

P. R. Viswanath ◽

S. R. Patil

Keyword(s):

Vortex Breakdown ◽

Delta Wing ◽

Aerodynamic Characteristics ◽

Surface Flow ◽

Flow Visualisation ◽

Symmetric Flow ◽

Gradual Process ◽

Wing Sweep ◽

The Mean ◽

High Angles Of Attack

AbstractAn experimental study investigating the aerodynamic characteristics of generic delta wing-body combinations up to high angles of attack was carried out at a subsonic Mach number. Three delta wings having sharp leading edges and sweep angles of 50°, 60° and 70° were tested with two forebody configurations providing a variation of the nose fineness ratio. Measurements made included six-component forces and moments, limited static pressures on the wing lee-side and surface flow visualisation studies. The results showed symmetric flow features up to an incidence of about 25°, beyond which significant asymmetry was evident due to wing vortex breakdown, forebody vortex asymmetry or both. At higher incidence, varying degrees of forebody-wing vortex interaction effects were seen in the mean loads, which depended on the wing sweep and the nose fineness ratio. The vortex breakdown on these wings was found to be a gradual process, as implied by the wing pressures and the mean aerodynamic loads. Effects of forebody vortex asymmetry on the wing-body aerodynamics have also been assessed. Comparison of Datcom estimates with experimental data of longitudinal aerodynamic characteristics on all three wing-body combinations indicated good agreement in the symmetric flow regime.

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